Speed of a Minibike: Jackass Number Two

Abstract

The purpose of this activity is to determine the minimum speed needed to
successfully complete the loop shown in the clip "The Mini Loop" from the 2006 movie, Jackass Number Two.

Introduction

Movie Synopsis

Famous from the MTV show Jackass, Johnny Knoxville, Bam Margera, Chris Pontius,
Steve-O, Ryan Dunn, and Jason "Wee Man" Acuna, come back to the screen
for an action packed theatrical movie. Jackass Number Two is a sequel of the original
Jackass movie in which a group of brave men come together to make a movie
solely based on crazy and dangerous stunts.

A minibike is a miniaturized version of a motorcycle. The four stroke motor
that runs the bike is similar to one of a lawnmower. The only difference
is that the shaft direction. They were first used as "pit bikes" so that
drag racers could efficiently travel to the pit stop. A decent minibike
can reach speeds of over 60 km/h and also attain a fast acceleration because of
its light body frame.

Mini-Loop

In this clip Ehren McGhehey and Thor Drake try to fully complete their homemade loop by riding on a minibike.

Procedure

Play the movie in DivX Player and find the scene where Danger Erhen is standing
right besides the loop.

Open WadRuler [exe] and take the coordinates from Danger Erhens head, toe, top of
the loop, and bottom of the loop.

Analysis

Knowing that Danger Erhen is 1.8542 meters tall we can find the diameter
of the loop. The distance between Danger Erhen's foot and toe is 6.62 centimeters
and the diameter of the loop is 8.73 centimeters. We can use ratios to
figure out the diameter.

Conclusion

We concluded that the minimum speed needed to clear the loop was 7.74 m/s (17.3 mph).

Sources of Error

One source of error was that there is air resistance on the rider and on the
bike. Therefore, the velocity needed to clear the loop would be greater. Another
source of error is that we calculated so that the bike
could complete the loop in a straight path. However, the bike is going in a
angle. Therefore, the bike needs more speed to clear the ramp.